1. Field of the Invention
The present invention relates to a bulb of an electrodeless lighting system, and particularly, to a bulb structure and a manufacturing method of an electrodeless lighting system configured to improve light distribution characteristics.
2. Description of the Background Art
In general, an electrodeless lighting system is an apparatus emitting visible light or ultraviolet light from an electrodeless plasma bulb upon applying microwave energy to the bulb. The electrodeless lighting system has a long life span and good lighting effect compared with an incandescent lamp or a fluorescent lamp which is generally used.
FIG. 1 is a longitudinal sectional view showing one example of a conventional electrodeless lighting system.
As shown, the conventional electrodeless lighting system using microwave energy includes: a case 1 forming a certain interior space; a microwave generator 2 mounted in the case 1, for generating microwave energy; a waveguide 4 for guiding microwave energy generated from the microwave generator 2; a resonator 4 installed at an exit portion 4a of the waveguide 4, communicating therewith; and a bulb 5 positioned in the resonator 6, for generating light as a filling material becomes a plasma by the microwave energy transferred through the waveguide 4.
In addition, a reflecting mirror 7 for concentratively reflecting light generated from the bulb 5 to the front is provided in front of the case 1, namely, at a surrounding area of the resonator 6.
Undescribed reference mark 12 is a bulb motor for rotating the bulb 5, and 12a is a bulb motor rotating shaft.
The bulb 5 includes; a bulb body 5a having a certain interior space and formed as a spherical shape; and a bulb rotating shaft 5b extending from the bulb body 5a and coaxially coupled to the bulb motor rotating shaft 12a, for serving as a medium for rotation of the bulb body 5a according to the rotation of the bulb motor 12.
FIG. 2 shows a manufacturing method of a bulb of the conventional electrodeless lighting system, and FIG. 3 shows a bulb structure of the conventional electrodeless lighting system.
As shown in FIG. 2, a hollow pipe 8 communicating with an interior space of the bulb body 5a is formed at one side of the bulb body 5a, the opposite side of the bulb rotating shaft 5b. 
A luminous material 9 is injected into the interior space of the bulb body 5a through the hollow pipe 8. After a proper amount of luminous materials 9 are introduced in the interior space of the bulb body 5a, the hollow pipe 8 is removed, and the portion communicating with the hollow pipe 8, of the bulb body 5a is covered. In this process, as shown in FIG. 3, a protrusion 5c is formed on the covered portion of the bulb body 5a. 
However, the bulb of the conventional electrodeless lighting system having such a structure has the following problems. Because the protrusion remains at the bulb portion in the manufacturing process, part of light passes through the protrusion and is refracted thereby when light is emitted from the bulb to the outside. For this reason, the light distribution characteristic of the entire electrodeless lighting system is degraded, and its appearance does not look fine.